Process and circuit arrangement for monitoring the function of a program-controlled circuit

Abstract

To monitor the correct function of a microprocessor, microcontroller or any other program-controlled circuit data processing results are checked in the working cycle for correlation with data which are produced independently of the circuit to be monitored and independently of the program run in a monitoring circuit. If deviations indicative of a malfunction occur, a disabling signal is generated. To this effect, data words or a data word sequence is produced in the program run of the circuit to be monitored and transmitted to the monitoring circuit at predetermined times. The content of the data words and the timely appearance of the data words is monitored by way of the monitoring circuit. (FIG. 2)

We claim: 
     
       1. A process of monitoring the correct function of a program-controlled circuit, comprising: during a working cycle of the program-controlled circuit, producing data words in the program run of the program-controlled circuit;   transmitting the data words to a monitoring circuit at predetermined times;   using the monitoring circuit to compare content and timing of the data words with predetermined data words and predetermined time intervals; and   based on a result of comparing the content and timing of the data words with the predetermined data words and the predetermined time intervals, determining whether a malfunction has occurred wherein the data words produced in the program run of the program-controlled circuit provide sequence of words, which are compared for correlation with a corresponding predetermined sequence of words by the monitoring circuit.   
     
     
       2. The process as claimed in claim 1, wherein the sequences of words in the program-controlled circuit and in the monitoring circuit are produced according to different algorithms. 
     
     
       3. The process as claimed in claim 1, wherein the monitoring circuit retrieves the predetermined data words from a memory. 
     
     
       4. The process as claimed in claim 1, wherein the monitoring circuit compares time periods between two successive data words with predetermined periods for correlation. 
     
     
       5. The process as claimed in claim 1, wherein the program-controlled circuit and the monitoring circuit produce data words in response to a recurring event. 
     
     
       6. A process, according to claim 5, wherein the recurring event is activation of an ignition of an automotive engine.